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Automatische TreinBeïnvloeding or ATB is a Dutch train protection system developed in the 1950s. Its installation was spurred by the Harmelen train disaster of 1962. ATB operates by the train collecting electrical signals from line-side apparatus and will override the driver's controls in the following situations: * a) failure to reduce speed at a caution signal (ATB will slow the train sufficiently to stop at the next signal). * b) failure to observe speed limit (ATB makes an immediate emergency brake application) Speed limits are set in 5 steps: 40 km/h, 60 km/h, 80 km/h, 130 km/h and so-called ''volle materiaalsnelheid'' (i.e., full speed allowed for that type of train), which can be 140 km/h at most for non-high speed trains. If the train's maximum allowed speed is lower, the 130 km/h setting is omitted. == Design limitations == One of the early system's design limitations is the inability to enforce restrictions stronger than a speed limit of 40 km/h. Several accidents at train stations and railroad yards occurred because the driver failed to stop at a red signal and ATB did not intervene, as it had already enforced a speed below 40 km/h. Strange as this limitation may seem, there was a reason for it. ATB works by sending electrical signals through the track. After passing a red signal and entering a section already occupied by another train, the track circuit is shorted by the other train and there is no signal any more. Therefore, the absence of a signal should be interpreted as the most restrictive signal, making the system fail-safe. To allow driving on sections not equipped with ATB or driving on sight onto occupied track, which cannot be discerned from passing a red signal using a system like this, this most restrictive electrical signal was defined as representing a speed limit of 40 km/h. The main purpose of ATB was to prevent overspeeding and failing to respond to yellow signals, as it was deemed unlikely any driver would miss a red signal when already traveling slower than 40 km/h and expecting one. As safety regulations have become stricter over time, it is seen as a problem now. Another problem is the maximum speed set to 140 km/h. Though there are tracks with a design speed of up to 160 km/h, they cannot be used up to full speed because ''ATB Eerste Generatie'' (ATB-EG, ATB First Generation) does not allow this. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Automatische treinbeïnvloeding」の詳細全文を読む スポンサード リンク
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